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Report Provides Weak Justification for Expansion of Newark Charters

BOULDER, CO (March 17, 2020) – A recent Manhattan Institute report attempts to estimate the effects of charter school enrollment on student test scores in Newark, NJ – a city whose charter sector has been under intense scrutiny – and finds positive effects on English language and math test scores. The report deems these effects “large” as compared to other types of educational interventions.

Dr. Mark Weber of the New Jersey Policy Perspective and Rutgers University reviewed Charter Schools in Newark: The Effect on Student Test Scores, which uses a random component of Newark’s school enrollment system to isolate the effect of charter schools on test score outcomes. 

The report’s method creates a natural experiment that compares outcomes between students who were offered charter seats and those who were not. This creates strong internal validity for the report’s positive test score findings. However, the generalizability of the findings is undermined by the fact that students who apply to charter schools differ significantly from the greater Newark student population. Students who are offered seats in charter schools are, for example, less likely to be English language learners or have special education needs. But the report never addresses this core issue of external validity.

The report also fails to address a key issue of scalability and sustainability. Teachers in the studied charter schools are less likely to remain in their jobs more than a few years, resulting in schools employing relatively few experienced teachers. This allows the schools to have lower overall personnel costs, even as they pay their inexperienced teachers more than comparably inexperienced public district school teachers, and even as they provide longer school days. 

More time in school, in all likelihood, will positively impact test scores. However, can the studied charter schools maintain this financial model as they expand and enroll a different student population? While the report confirms previous work showing a positive charter effect on test scores in Newark, it fails to address these and other critical issues that stakeholders must understand to formulate good charter school policy in New Jersey and elsewhere. 

Accordingly, even for policymakers who equate test scores with overall learning, Weber concludes that while the report has credible internal validity, it has only limited policy use.

Find the review, by Mark Weber, at:

Find Charter Schools in Newark: The Effect on Student Test Scores, written by Marcus A. Winters and published by Manhattan Institute, at:

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